Universal Oxygen
by September Severtana
Summary: "You came to me in microscopic molecules of air. Even when my world was falling apart, you let me breathe." In which Sherlock is Earth, John is oxygen, and addiction is the state of denial before love.


**I missed the Universe oneshots, so I did some research and came up with this.**

* * *

My dearest John,

I hope you know that I consider your violence against me to be less than I deserve, but it's for a rather selfish reason, first and foremost. Only later did I come up with the other reason: I left you all alone and grieving, which I actually know about, and you do not need nor deserve that. I've spent more time thinking about why I feel so weighed down and sad since I got back, and perhaps it is only to do with hurting you, but I am a selfish person, I have realized. I'm a child that wants what they cannot have and does nothing to remedy that. Also, I am an addict that just got a taste of what they've been missing. You are so addictive, John, that I've figured out how to tell you.

I have to start from the beginning, as that is the best place.

I was created slowly, molecules of gas and cosmic dust piecing together because of static electricity, sometimes even molecules that didn't want to be a part of me. Everything inside me conflicts, you see. With every thought comes a counterpoint, and only other people are simple and without counters. You aren't. You are a source of conflict in that I still don't know you. I learn new things about you, John Watson, every day I am with you. I need it. I don't think you realize how much I need it.

There was such a long time in creation, such a long time of conflict, but it didn't get better as everyone said it would. 30 million years into my creation, I melted down. Poison can be so slow that not even I have the ability to fight it until it doesn't even matter anymore. And I was poisoned. People saw me as a freak, they called me a psychopath that couldn't feel, they hurt me and cut me and bruised me and I just...dissolved into a planet of fire and magma. I had nothing, and so I burned with the heat of the Sun.

I do have emotions. They haven't helped me much, but I need them to need you. It's dreadfully complex, and I'm normally good at deducing complexity, but it's different now.

 _We_ are different now.

Eventually, my pain and fire and heavy elements sunk to my core. They hide there, still burning, still too hot and volatile for me to handle without a great deal of traveling through the locked rooms of my mind palace. I need more time. I don't seem to have it.

You see? It really is all about me, isn't it? I'm sorry. I just want you to understand.

On the outside, my shell hardened. It didn't take very long, what with the darkness of space being a vacuum with no temperature and my surface being thousands of degrees. Only a few million years or so, perhaps less. I was so basic then; _life_ was so basic then. That shell protected me, until I didn't want it to. What you do to me, John Watson, is unlike anything else. I'm sure I shall reiterate myself a dozen times over the course of this letter, but why not preach the truth? It is what I thrive on, after all.

I feel so old, John. You are older than me in age, but in soul I am ancient. I have seen too much and known too much, and I grew up too fast, yet slower than any human can imagine. Billions of years, and I still have so much farther to go, but I don't want to go without you.

I'm getting off track; I have a point later on, if you'll just stay with me.

You came to me in microscopic bits of matter. Even when I couldn't see anything good about my world, little pieces of you would touch me one drop at a time, for a billion years. I didn't know you then, but it wasn't of any consequence. You were the quiet voice echoing through my halls that told me to keep going, to keep living. I still know those words were yours, because you exist everywhere to me. John, you are _life._

As I aged, I discovered that living things had taken their place on me, something I never thought would happen in my too-long lifetime. In my oceans grew young animals and plants. I was finally becoming the blue planet that you knew me as before I left.

My leaving...well, let's just say it killed us both. It's horrifically amazing how humans can die inside without being physically dead.

You know that I had to leave you. Moriarty was going to kill you, and I couldn't let that happen. The possibility never even crossed my mind. But as I fell, and I realized that my brother was going to save me, the flora and fauna that I had cultivated on my surface for over three billion years (more years pass with you in my life) died in one fell swoop. The only explanation that imbecilic people could come up with was that a meteor had struck me and the cloud of ash blocked out the sun. It's a convenient lie.

All those species became extinct because you and I were separated.

Being selfish, I needed to have you back, breathing air into my lungs, pouring water onto my deserts, breaking through the rain with sunshine. I simply _need_ you. So I found you as fast as I could, rushing back into your routine and smashing through everything you had created while I was gone. Planets aren't known for subtlety. I really am sorry for that.

Now, I'm back to being an addict. I suppose being addicted to oxygen is not considered an addiction among humans because you need it to live, but it considered as such among planets. I take you from your life without asking, and this seems to make it a battle between my primal instincts to take what I want, and the emotional portion of my brain that is severely damaged every time I hurt you. I hurt you when I walked into that restaurant and stole you away from the life that you had built for yourself, and for that, I deserve more than a few punches.

The conflict has never stopped, has it?

This explanation has turned out longer than I meant it to be, and also full of planetary metaphor, but I need you to know that I will always need you, John. Nothing can change that now, especially not after billions of years. But no matter how much I need you (and I'm going to scribble this down so that this weight on my shoulders can lift) and love you (you see? I feel happier already), I will leave you alone if that is what you want. Need can be combated, no matter how long it takes.

(I'm lying. My heart can't work without you, and isn't that the very definition of oxygen?)

I can live without oxygen, without my addiction to you, without your smiles and laughs, without your voice, without your life entwined with mine.

(Why do I keep lying to you? I love you and I can't let you slip through my fingers.)

Until my end,

William Sherlock Scott Holmes

* * *

John walks to 221B from Mary's house. He can't consider her house to be home, he has always known that, and now he has no reason to. Sherlock will be inside, probably reading or lying on the couch with an arm thrown over his eyes. He looks so tired lately. It worries John, even though he tries to convince himself that it doesn't. But Sherlock won't sleep, especially if he needs to.

He knocks on the door, like he's a guest rather than a resident. As John opens the door, he sees a colossal mess of books, test tubes, blankets (nearly all of them that Mrs. Hudson owns), and crumpled up sheets of paper, covered in Sherlock's neat scrawl. John can't find his laptop or any food in the kitchen, so he slowly walks through the rooms in a sort of trance. Nothing has changed really, just a lot more clutter than he remembered. All of his clothing and personal items are untouched, except his favorite oatmeal-colored jumper that has been folded and unfolded and refolded numerous times. John leaves his room and comes back down the stairs to the main part of the flat, realizing where Sherlock is.

John finds Sherlock curled up in the bathtub, hugging himself tightly. John would use another word to describe it, but there isn't one. The other man looks asleep, and that is what really tips John off to how wrong the situation is.

Sherlock only takes out blankets on danger nights, when he feels so cold it's like the planet froze over. The man may not be tidy, but that level of disorganization had shown up exactly once: the days after Moriarty had tried to blow him up. John's jumper is most telling of all, because unfolding it and refolding it that many times was a symptom of obsession. Obsession + danger night + fear doesn't equal a pretty picture. It scares John so much that Sherlock could have gotten this bad while he was gone.

He shakes Sherlock's shoulder with all the gentleness he used with children. "Sher. You have to wake up now. I'm here to take care of you."

"Go 'way, Mycroft," the other man mumbles, hiding his face in his hands. "I don't need nobody takin' care of me."

"Sherlock, can you stand?" John asks, refusing to leave, or to get the doctor-tone out of his voice. "I'll help you if you need me to."

"Myc never wants to help me, just blah blah blah in my ear." Sherlock giggles hysterically. "You're not Mycroft at all, are you?"

"No. I'm not Mycroft. Do you know who I am?" This is getting worse by the second, but John physically can't leave Sherlock like he is. He runs through the possibilities of what could be wrong, but then stops. He has to focus on making Sherlock well again.

Sherlock thinks for far too long before saying, "You're my John."

He breathes a sigh of relief. "Yes, I am."

"But are you the _really_ real John? There's so many that aren't, I've lost count. Can you prove it to me?"

John forgets all of his doctor protocol and climbs into the tub with Sherlock. It's a bit of a tight fit, but John stopped caring a little while ago. His arms snake around Sherlock's too-thin figure and Sherlock nestles close to him, pressing the smallest kiss to John's neck. They lay together like that for a long time, John reassuring himself with the feeling of the other man's body against his. Sherlock is there, Sherlock is safe, Sherlock is alive, John chants inside his head. Everything is calm.

"John?" Sherlock asks in the softest whisper. "Did you know that I'm suffering from withdrawal?"

"What?"

"I mean that over my time destroying Moriarty's web, I ingested more cocaine than in all of my college years. Ever since I've been back, I haven't taken any, but withdrawal shocks the body and turns it against itself. Common symptoms are irritability, exhaustion..." His voice dissolves into a murmur John can't hear.

"Why on earth did you do that, Sherlock? There is no rational reason to return to a bad habit." John is trying to stay calm for his own sake, but he's failing, and it _hurts._

"Rationality has nothing to do with love nor addiction. They both creep up on you slowly, like the darkness after a sunset." Sherlock walks two fingers over John's arm, up to his shoulder, and back down again.

"What does love have to do with addiction?"

"Sometimes love starts out like that. Addiction is the stage of denial the person goes through when they are convincing themselves it's just a bad habit. It becomes love when the person admits it to themselves. It took me far too long to get there." Sherlock turns his face into John's chest and refuses to answer any of his other questions. He instead amuses himself by carding his long fingers through John's hair. Sherlock seems to be memorizing John by touch, and it is relaxing, but too frightening to contemplate how far Sherlock has fallen to end up here.

"We need to get out of the bathtub," John says.

"Only if you promise not to take me to a hospital," Sherlock replies stubbornly. "Just because I haven't eaten in a few days or drank water doesn't mean I'm dying. I was dying before. Not now."

John says he won't while reaching into his back pocket for his phone to text Mycroft. _Sherlock is sick, suffers from withdrawal, and hasn't eaten in days. I'm scared. Please call him an ambulance. -JW_

Mycroft answers almost instantly. _Of course. It should be there in a few minutes. -MH_

* * *

The EMTs end up receiving no fight from Sherlock as they get him onto a gurney. He's unconscious.

John rides in the ambulance with him all the way to the hospital, never letting go of his hand even though Sherlock probably can't feel his grip. It's okay. Only John needs to know how long he's been here, how fast the hours pass. In the grand scheme of things, time doesn't really matter.

The hospital is filled with beeping that John had forgotten. People bustle by John and the gurney carrying Sherlock without a second glance, lost in their own little worlds of pain. John can see it in their eyes. The EMTs take Sherlock away from him until he stabilizes, and John feels the loss suddenly, like he's missing a limb again. Hallways form endless white tunnels to the room where the nurses are keeping his friend. He walks through doors numbly, remembering how many security guards it took to keep him from rushing into Sherlock's too-pale, pockmarked arms.

He can't let go of Sherlock again. It's not healthy, he knows that, and even though he should be thinking about what he's going to tell Mary, he isn't.

John's only thoughts are if he always needed Sherlock next to him like he needs oxygen to breathe.

* * *

The morning dawns cold and clear, Sherlock's eyes opening with the strange sensation of a weight on his chest. It takes a moment for his sight to adjust to the light, but when he does, he notices that John had fallen asleep on him. The two of them are in a hospital, he knows what those look like, and John is sleeping soundly, a hand entwined through Sherlock's and a soft breath escaping his lips.

"John," he whispers.

His friend stirs slightly, huffing and curling closer to him, and then settling again.

A tiny smile crosses Sherlock's expression. Maybe he should go back to sleep as well.

But just as he decides to do so, a nurse walks in. She starts speaking, but he shushes her and points to the sleeping man on his chest. She grins brightly and puts a finger to her lips in mock silence.

"You gave a few people quite a scare, Mr. Holmes," she says quietly. "Including your partner there. He barely left your side the whole night."

Sherlock runs his other hand through John's hair. He quite likes doing that. "I know. What can I do to get out of here?"

"You really need to sleep more, and eat more, and you should also never do drugs again. I know it's hard, and I know addiction is a difficult thing to get through, but it cannot control your life anymore, especially if you want to take care of him."

He shakes his head. "Now that he's back, I have no need for anything else."

"Good." The nurse briskly fiddles with some medical instruments in her bag and comes up with a blood pressure cuff. Standard procedure, she says, but Sherlock just wants her to go so he can stay with John.

When she finally clears the room, Sherlock breathes a sigh of relief. John hasn't woken up yet; his eyelids flicker as if he's dreaming.

The letters are still all over the sitting room floor, Sherlock realizes. Everything he wrote to John that he would never end up sending is still covering the ground for Mrs. Hudson or any common burglar to find. And yet, Sherlock can't bring himself to care. Let the mountains and valleys ring with the proclamations written then! Or at least the streets of London. John deserves to know how he feels about him. John always deserved that.

Sherlock gently kisses John's forehead, prompting the smaller man to blearily look up at him. "John?"

"Yes, Sherlock?"

"I love you."

And John smiles. "Alright. I forgive you for scaring me." He climbs on top of the hospital bed with Sherlock.

"Do you love me too?" Sherlock asks once they're both comfortable.

"Yes. I love you too."

"It's not just an addiction anymore, is it?"

"No."

"I'll have no more addictions than you."

"Neither shall I."

* * *

Sherlock goes home a few days later, hand in hand with John. Mary left them alone after she visited Sherlock at the hospital, saying she knew all along who John truly loved. She waved happily at them, and both men are perplexed about that, but too content with their lives now to care.

The drugs are gone, and the withdrawal is still the bane of Sherlock's existence, and he complains about it daily. John kisses him and laughs until Sherlock laughs with him. They promise to never leave the other without actually saying anything, but that's really the best way to do it.

The letters remain in a box in Sherlock's bedroom, unread and unorganized, the writings of a man who missed someone too much. He's gone now. What's left is a living, breathing planet, still addicted to oxygen.

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 **Hope you enjoyed. Read + review!**


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